tcp_timer.h

/* * Copyright (c) 1982, 1986, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 * tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp */#ifndef _TCP_TIMER_H_#define _TCP_TIMER_H_/* * Definitions of the TCP timers. These timers are counted * down PR_SLOWHZ times a second. */#define TCPT_NTIMERS 4#define TCPT_REXMT 0 /* retransmit */#define TCPT_PERSIST 1 /* retransmit persistence */#define TCPT_KEEP 2 /* keep alive */#define TCPT_2MSL 3 /* 2*msl quiet time timer *//* * The TCPT_REXMT timer is used to force retransmissions. * The TCP has the TCPT_REXMT timer set whenever segments * have been sent for which ACKs are expected but not yet * received. If an ACK is received which advances tp->snd_una, * then the retransmit timer is cleared (if there are no more * outstanding segments) or reset to the base value (if there * are more ACKs expected). Whenever the retransmit timer goes off, * we retransmit one unacknowledged segment, and do a backoff * on the retransmit timer. * * The TCPT_PERSIST timer is used to keep window size information * flowing even if the window goes shut. If all previous transmissions * have been acknowledged (so that there are no retransmissions in progress), * and the window is too small to bother sending anything, then we start * the TCPT_PERSIST timer. When it expires, if the window is nonzero, * we go to transmit state. Otherwise, at intervals send a single byte * into the peer's window to force him to update our window information. * We do this at most as often as TCPT_PERSMIN time intervals, * but no more frequently than the current estimate of round-trip * packet time. The TCPT_PERSIST timer is cleared whenever we receive * a window update from the peer. * * The TCPT_KEEP timer is used to keep connections alive. If an * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, * but not yet established, then we drop the connection. Once the connection * is established, if the connection is idle for TCPTV_KEEP_IDLE time * (and keepalives have been enabled on the socket), we begin to probe * the connection. We force the peer to send us a segment by sending: * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> * This segment is (deliberately) outside the window, and should elicit * an ack segment in response from the peer. If, despite the TCPT_KEEP * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE * amount of time probing, then we drop the connection. *//* * Time constants. */#define TCPTV_MSL ( 5*PR_SLOWHZ) /* max seg lifetime (hah!) */#define TCPTV_SRTTBASE 0 /* base roundtrip time; if 0, no idea yet */#define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */#define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistence */#define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */#define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */#define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */#define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */#define TCPTV_KEEPCNT 8 /* max probes before drop */#define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value *//* #define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) *//* max allowable REXMT value */#define TCPTV_REXMTMAX ( 12*PR_SLOWHZ) /* max allowable REXMT value */#define TCP_LINGERTIME 120 /* linger at most 2 minutes */#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */#ifdef TCPTIMERSchar *tcptimers[] =
{ "REXMT", "PERSIST", "KEEP", "2MSL" };
#endif/* * Force a time value to be in a certain range. */#define TCPT_RANGESET(tv, value, tvmin, tvmax) { \ (tv) = (value); \ if ((tv) < (tvmin)) \ (tv) = (tvmin); \ else if ((tv) > (tvmax)) \ (tv) = (tvmax); \}externint tcp_keepidle; /* time before keepalive probes begin */externint tcp_keepintvl; /* time between keepalive probes */externint tcp_maxidle; /* time to drop after starting probes */externint tcp_ttl; /* time to live for TCP segs */externint tcp_backoff[];
struct tcpcb;
void tcp_fasttimo _P((void));
void tcp_slowtimo _P((void));
void tcp_canceltimers _P((struct tcpcb *));
struct tcpcb * tcp_timers _P((registerstruct tcpcb *, int));
#endif